Well, well, well. We all know Apple's App Store policies are incompatible with the GPL, and as such, software using this license can't be distributed in the App Store. So, what about Microsoft's Windows Phone 7 Marketplace? Well, whereas the App Store doesn't specifically mention the GPL (Apple's terms are simply incompatible), Microsoft drops the pretence and simply bans GPL and GPL-esque licenses outright.

Like the App Store, the Marketplace is also governed by a number of terms, and in those, Microsoft makes it very clear - without mincing words - that it doesn't want any GPL'd code in the Marketplace. Article 5, point e of the Application Provider Agreement is what it's all about.

"The Application must not include software, documentation, or other materials that, in whole or in part, are governed by or subject to an Excluded License, or that would otherwise cause the Application to be subject to the terms of an Excluded License," it states.

This item is useless by itself, since it's not yet clear what an Excluded License is. Well, this term has been defined at the beginning of the document, and there, Microsoft makes it quite clear.

"Excluded License" means any license requiring, as a condition of use, modification and/or distribution of the software subject to the license, that the software or other software combined and/or distributed with it be (i) disclosed or distributed in source code form; (ii) licensed for the purpose of making derivative works; or (iii) redistributable at no charge. Excluded Licenses include, but are not limited to the GPLv3 Licenses. For the purpose of this definition, "GPLv3 Licenses" means the GNU General Public License version 3, the GNU Affero General Public License version 3, the GNU Lesser General Public License version 3, and any equivalents to the foregoing.

You can't really get much clearer than that, can you?

This is obviously not cool, but from the wording it becomes clear that this is not some super dastardly plan to destroy the GPL (I'm out of tinfoil, sadly), but more about covering their bases. Since Microsoft is a distributor of the software in question, it must also comply with the GPL; it must make the source code available upon request if someone so desires. I think Microsoft simply doesn't want to deal with that - in the same way Apple doesn't want to deal with it - and as such, prohibits you from distributing GPL code through the Marketplace.

While I'm actually quite sad about this, I do have to give them one prop for being clear, open, and honest about it. Of course, they'd get massive props if they came up with a way to make GPL code compatible with the Marketplace.